The research proposed focuses on two strategies to control HIV-1 infection and explore the basic biology which occurs between 2-5OAS, PKR, and HIV-1. First, nuclease-resistant, non-toxic, biologically active 2-5A derivatives and their lipophilic conjugates have been synthesized to augment the depleted 2-5A cellular pool by acting distal to the 2-5OAS blockade in HIV-1 infected cells. These 2-5A derivatives show enhanced uptake in HIV-1 infected cells. They may act, in part, through the activation of RNase L leading to an inhibition of HIV-1 replication. This antiviral effect of the 2-5A derivatives on HIV-1 replication may only represent one aspect of their mode of action in vivo; therefore, alternative mechanisms of activity will be examined, including inhibition of HIV-1 integrase and HIV-1 reverse transcriptase. The selectivity of the 2-5A derivatives will be tested by measuring their effect on host cell DNA, RNA and protein synthesis in HIV-1 infected and uninfected cells. Second, cDNAs encoding 2-5OAS and PKR have been cloned under the control of the TAR structure located within the HIV-1 3' LTR and packaged into high titer retroviral vectors. Once eukaryotic cells are stably transduced, these key antiviral enzymes will have been placed under this alternate control mechanism. Upon infection, the HIV-1 produced Tat protein will transcriptionally activate the TAR sequence leading to the increased production of 2-5OAS and PKR. Subsequent activation of these enzymes by viral dsRNA may ultimately lead to the destruction of the infected cells preventing viral spread and/or latency reactivation. This proposal will therefore focus upon the understanding and restructuring of the mechanism(s) by which the natural antiviral host defense pathways control HIV-1 replication.